Effects of bromination on anthryl-capped DPP-based semiconductor materials: Improved electrical characteristics of organic field-effect transistors

Diketopyrrolopyrrole (DPP), typically flanked with thiophene rings as pi-spacers, has been regarded as a prom-ising electron-acceptor unit for constructing donor-acceptor-donor (D-A-D) type small molecule organic semi-conductors. Exploring the relationships between its conjugation structure and semiconducting property is of great importance for both molecular design and device fabrication of such DPP materials. Herein we describe the synthesis, self-assembly, and transistor characteristics of two novel N-and N '- 2-octyldodecylated DPP de-rivatives which were modified with native anthracene (An) and brominated anthracene (Br-An) at 5-, 5 '-position of the flanked thiophenes, respectively, namely An-DPP and Br-An-DPP. Attributing to the self-assembly be-haviors, they exhibit enormous difference in hole transport characteristics on interdigitated-electrode based organic field-effect transistor (OFET) devices even though there is only two atoms' discrepancy in accordance with their molecular structures. The characterization of OFETs with interdigitated-electrodes based on Br-An -DPP reveals p-channel operation with highest field-effect mobility of 0.2 cm2 center dot V-1 center dot s- 1, which is 107 times higher than that of An -DPP (4.8 x 10-8 cm2 center dot V- 1 center dot s- 1), and with a threshold voltage of -2.5 V. X-ray diffraction, atomic force microscopy, scanning electron microscopy, and optical absorption studies reveal the presence of crystalline films caused by bromination on anthracene-modified alkylated DPP (i.e., Br-An-DPP), while An-DPP exhibits completely amorphous phase.

Automated summary

By modifying the side chains of DPP molecules with different anthracene groups, it has been found that the charge transport characteristics on organic field-effect transistor devices can be significantly altered.